Back when borders were relatively firm and international travel was rare (extremely rare in comparison to today) it was less of a threat.
Today, we live in a world where a coronavirus or other pathogen from one bad animal in one wet market could potentially kill tens of millions or more throughout the world. This must be one of the lessons learned from this pandemic.
Different regions in the world have some immunity to such pandemics that might mask it long enough to get a foothold. One example of this is the current pandemic, which has had an outsized impact on ethnic groups the furthest from the center of the pandemic. It is fair to say based on data analysis that Asian cultures and populations had some protections against this pandemic likely from more exposure to similar viruses and lower BMI’s.
Africa has some very really scary ones as well. The same things occur in the plant world. The oak blight in Ohio for example might decimate the oak trees in the mid-west but have little impact on those in the south as a hypothetical.
Yeah, when I think where I have traveled to without ever really thinking about diseases, it’s kind of spooky. I did get the recommended vaccines against some things (not common vaccines so you have to go to a special pharmacy here that inoculates against the more exotic diseases) but in hindsight I think I have been lucky.
The only place where I had a real problem was northern Vietnam. I started developing skin rashes and infections right after I got off the plane. A couple got pretty gruesome. And then they started going away when we got to Cambodia. I actually attributed it to something in the Vietnamese water or air pollution. Hanoi has horrible air pollution, at first you think it’s fog but you realize after a day when it’s still there it’s smog.